1. Field of Invention
This invention is directed to the field of metal forging and, more particularly, to methods and apparatuses for near net warm forging relatively small, complex-shaped parts.
2. Description of Related Art
Many relatively small, complex metal parts, such as automotive rocker arms, are presently primarily formed and manufactured by stamping. For complex shaped parts, this stamping process requires several mechanical operations or steps to produce a single part, and results in parts with large radii at angular surface transitions (such as vertical-to-horizontal) due to the inability of metal stamping equipment and processes to form sharp angles at surface transitions. Further, certain part shapes cannot be formed by stamping.
Another known method of forming and manufacturing such relatively small, complex metal parts is investment casting. While parts made by investment casting may have more precise transitions between surfaces (i.e., smaller radii at surface transitions), such parts cannot be as efficiently mass produced by investment casting. Further, it has been attempted to manufacture such relatively small, complex metal parts by sand casting, but with little success.
In addition, certain relatively small, complex metal parts can also be machined from stock material. However, this manufacturing process cannot be used to efficiently mass produce such parts, as at least several complex machining operations or steps are required to produce a part. Thus, this method is typically used only to produce high-performance specialty parts such as specialty rocker arms made, for example, of special lightweight alloys.
Hot forging methods and apparatuses have also been used to produce such relatively small, complex parts. Forging offers certain advantages over casting. For example, a forged part is usually "stronger" than a casted part, because the forged part has reduced porosity and a more refined internal structure. However, hot forging methods and apparatuses have certain disadvantages, as follows. First, parts made by hot forging must have draft angles on all vertical surfaces to facilitate removal of the parts from the molds after forging. The formation of these draft angles requires excess material to form the parts, unnecessarily increasing the cost of the parts and overall mass of the engine's valve train. Second, during hot forging, flash (or excess material) is formed between die segments, forming rough edges that must be subsequently machined. These subsequent machining operations increase the cost of the parts.
Thus, while hot forging methods and apparatuses can be employed to mass produce certain relatively small, complex metal parts, the cost of producing such parts by these methods and apparatuses is relatively high due to these disadvantages. Cost is very important in producing certain mass-produced, relatively small, complex metal parts, such as automotive rocker arms. Any cost saving or reduction is important, even if minimal, because of the volume of the parts which are usually produced by a manufacturer.
Accordingly, there is a general need for methods and apparatuses that can efficiently produce relatively small, complex shaped parts such as automotive rocker arms, and which are cost effective. This general need includes a specific need for methods and apparatuses that produce such relatively small, complex shaped parts in one or a small number of mechanical steps and which produce parts that do not require extensive machining. Further, there is a need for methods and apparatuses which produce such parts wherein the completed parts have finely machined surfaces and small radii between surface transitions.
It is an object of the present invention to provide such methods and apparatuses. It is another object of the invention to provide methods and apparatuses which can produce complex parts such as automotive rocker arms with substantially no waste of material.